The present invention relates to improvements in pneumatic tires having crown belts, which are intended for fitting to vehicles capables of travelling at high speeds, of the order of 200 to 300 km/h, such as touring cars and sports or competition cars.
Experience which has been gained in recent years has shown that a type of crown belt which is particularly suitable for such tires is that in which the lateral edges are folded over and flattened against one of the faces of the belt. Such belts are more resistant to the stresses and faults caused by travelling at high speed. However, it has been found that apparently minimal changes in the dimensions selected for the belt (the width of the belt and the relative width of the folded edges), in the materials selected for use (more or less flexible textile or metal cords), and in the angles of inclination selected for the cords relative to the longitudinal direction of the belt, have a very substantial effect both on the ability of the tires to stand up to high speeds and on the often conflicting qualities of roadworthiness which they are called upon to exhibit, such as a good ride (in particular on poor roads), road holding in a straight line and on corners, and the speed and uniformity of tread wear.
The invention proposes improved embodiments of belt of this kind with folded edges, which make it possible to achieve not only an excellent ability to stand up to high speeds but also a very good compromise between the various qualities of roadworthiness required, while at the same time being very easy to manufacture.